text:
Is there a way to approximate the best glide speed for maximum glide distance in a headwind during flight?
Flying at an airspeed corresponding to an aircraft's maximum glide ratio in calm air will maximize the distance covered for a given altitude (AGL).  But in a headwind, the horizontal velocity would be reduced by the headwind velocity and the maximum distance at that airspeed would be correspondingly reduced.  At an extreme case, if the headwind is greater than the best glide speed, an aircraft would move backwards relative to the ground if it flew at best glide speed.  But an aircraft could always pitch for a greater airspeed into the wind an achieve some forward distance even if the headwind was greater than the best glide speed.
My question is how to determine the best "penetration" speed if one is forced to try and glide for maximum distance into a headwind?  And can this be approximated in flight?
I am mostly interested in small GA aircraft that might be considering a forced landing, so time is of the essence.  A corollary question would be above what headwind speed is it best not to try for any distance and only consider landing in the downwind direction.  I understand that maximum range would always be downwind, but for some small headwind speeds and enough altitude, an upwind landing location might still be practical.

I wouldn't try to glide long distances with a headwind, technically if you have a ways to go, turn to a tail wind and pitch for best glide. That will give you the most ground distance. Best glide speed is best glide speed, it doesn't change based on headwind.

It's determined by offsetting the polar curve for the aircraft (https://en.m.wikipedia.org/wiki/Polar_curve_(aerodynamics)), although that's not handy in an emergency! In gliding I've been told that adding half the wind speed to the minimum sink rate is a reasonable approximation. I would concur though that flying downwind at min sink allows you to cover most ground when looking for a suitable landing site.


text:
How much force are large aircraft brakes able to exert?
In a comment left on my answer here Jan Hudec says:

Note that usually on dry surface the brakes exert much less force than the tires could handle.

This got me wondering how much force large aircraft brakes can provide.
The limiting factor in brake force for a vehicle is the friction between the tire and the surface. On my car, even on dry pavement, the brake force available is always greater than the tire/ground friction, so I can always lock the brakes and set off the ABS. I may be misunderstanding it, but Jan’s comment makes me think that maybe large aircraft don’t have that much brake force available. If you commanded maximum braking on a dry runway would the brakes try to lock? Is the ABS really only necessary on a contaminated runway?

Yes, they can lock the brakes up, and some (many large/commercial) aircraft have anti skid systems much like vehicle ABS.

Related: This question. In @Federico 's answer, there is a link to this presentation. See page 16 and next.

Under normal use case I'd say it's indeed pretty far. Say dry surface with u=0.7 then you only need less than 450 meters to stop at 150 knots, and 700 meters for wet surface whose u=0.4, but usually for a plane that lands at that speed would have ~2000 meters to use. Even for a plane with 215 knot touch down speed(the worsts, like space shuttle, SR71,XB70,B58 are all around 175-185 knot range), with u=0.4 it would still be able to stop within 1500 meters. I don't know what kind of worst case ABS is planning for but for dry surface normal operation I don't think it is ever triggered.

However jet fighters seems to break traction limit regularly: even if they can lock the wheels, the engine can still push the fighter forward at full thrust (engine can provide close to 1g of acceleration while tires can only neutralize at most 0.7g of it). When they take off from sky-jump carriers there are wheel blockers that keep the plane still  before taking off rather than relying brakes.

@RonBeyer: And which predate automobile ABS by a decade or so, and are the direct ancestors of same.

This has been answered before, but in a different context. Therefore, I copied the essential part here:
Emergency procedures at take-off weight will produce the biggest braking loads. I will calculate the highest possible braking loads for a Boeing 747-400 that weighs up to 400 tons on take-off. For this I need this plot of a polynominal for the braking coefficient, which is the ratio between vertical and horizontal forces before the tire skids. I do not know the source; I collected it somewhere in the past and never found a reason to doubt its validity.

Shortly before the aircraft comes to a stop, the highest friction coefficient is reached, and then little lift is produced by the wings, so the vertical tire loads are those of the static case. The braked wheels are the 16 main wheels; I assume that the unbraked noswheels carry 4% of the total weight. At 96% of 400 tons acting on those 16 wheels, this is 24 tons = 235,344 N = 52,907 lbs of downward force per wheel. Since the friction coefficient is 1 at low speed, the same load is transferred horizontally from each wheel to the ground and into the gear struts.
And, yes, brakes will lock on a dry runway if the disk brakes are fully engaged.

I read Jan's comment as stating that the tyres will remain intact when maximum braking force is applied on a dry runway: tyres are dimensioned such that they don't fail structurally from maximum braking effort.
They can fail thermally, after a blocked tyre has skidded at high speed for a while, and the resulting high temperature at the contact area eats through the tyre rubber. This is of course one of the reasons why anti-skid systems are implemented in aircraft, the other reason being that rolling friction is higher than skidding friction. This report describes what goes on when tyres skid, the high temperature causes part meltdown and gasification of the contact area, which provides a form of lubrication and therefore a lower resulting friction coefficient.
Without an anti-skid system, the brakes can most certainly lock up the wheels, and in fact car ABS systems were implemented decades after they had been installed in aircraft, as mentioned in the wiki. As to the maximum braking force acting on the aircraft mass, Torenbeek page 585 lists the maximum deceleration values as typically:

0.55g: dry runway, maximum effort, ignoring passenger tolerance
0.35g: wet runway, modern braking with anti-skid, lift dumpers, reverse thrust
0.15g: wet runway, simple braking or flooded runway, reverse thrust

That’s the way I am reading it too, that the brakes are not designed to have more braking force than the tires on a dry runway. On a wet runway they can, therefore you need anti-skid. I just wasn’t sure if they were usually designed that way or not.

The amount of force required (in many cases they are designed to deliver more force but this provides a minimum) is based on the aircrafts weights and speeds, you can find most of the info in

§ 25.735 Brakes and braking systems.

The most relevant section is that you need to be able to provide enough force to decelerate within limits

...The energy absorption rate derived from the airplane manufacturer's
  braking requirements must be achieved. The mean deceleration must not
  be less than 10 fps2.

Also as a matter of certification the brakes must be able to provide enough force to hold the aircraft in place on the ground under full thrust from the engines.

It would be helpful to provide an estimate of the force based on these requirements.

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What are the performance trade-offs in the Icon A5 spin resistant airframe?

I've been looking at the website for the Icon A5 amphibian LSA and noticed the wing section clearly has two different cross sections, presumably to facilitate the stall and spin resistance of the aircraft.  One of the videos on the site shows the wing as it stalls and the tell-tales attached to the wing clearly show the flow separation for the inboard section of the wing while the outer section still indicates attached flow.  I would guess that this wing must have either some performance trade offs or else it's a significant cost, otherwise why wouldn't most GA aircraft have this feature?  Perhaps fabrication in sheet metal would be difficult as I believe this aircraft is mostly composite construction.

Though performance details of the aircraft are not available, there seems to be a significant weight penalty associated with making the aircraft spin resistant.
It appears that the aircraft had to get a specific exemption for increased MTOW (1680 lb as against 1430 allowed) due to the incorporation of spin resistant design. Note that the weight given by the manufacturer is 1510 lb, still more than allowed.
As required in the exemption, the aircraft had to be fitted with a ballistic recovery complete-aircraft parachute system, affecting the payload. The engine power is also limited to 135 hp. The range is also low (~300nm).

Not sure if the weight is due to the wing design, but I guess an overall aerodynamic penalty is incurred by wing twisting.

Yeah I would tend to think the weight issue is more a result of the amphibious design rather than the wing.

Perhaps worth noting too that with two airfoils, by definition you cannot be using the most efficient airfoil - there's going to be at least some level of drag penalty

As of 2020-07, the Icon A5 Specifications page says Range: 427nm (45 min reserve).

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text:
What unique challenges/limitations will I face if I start a career as a pilot at 45 years old?
I'm contemplating a mid-life career change. I made some money in another industry, and now have the luxury of choosing a job that pays less, but provides enjoyment and satisfaction. I suspect being a professional pilot could be the ticket. I'm currently an active glider pilot with 300+ hours, and I am just loving it! I learned to fly gliders very quickly and I am confident that I could learn to fly powered aircraft quickly as well. Fortunately, I can afford the training and the cost of building up hours, potentially in my own plane.
I know it takes a long time to work up to flying an airliner, but I'm not sure that's even what I want to do. Flying smaller planes appeals to me more.
Am I crazy to try to start a piloting career at my age (45)? Is the system going to be biased against an older trainee like myself? Should I go to an aviation college? Will I ever make a decent salary given how many working years I have left? Also, see the question in the title. Thanks.

Challenges? Coming up with $60,000+, spending 6+ years getting your ATPL and working as a CFI to build hours only to be 12 years from mandatory retirement and being relegated to working as a first-officer for low-paying regional airlines. I'm not saying "don't do it", but certainly don't do it for financial reasons. The first 5-8 years of an airline pilot are extremely hard (low paying). Many pilots share apartments to get by.

Which country are you in?

I'm in the USA.

Wow, thanks for the impressive answers so far. It was hard to choose one as the accepted answer. I've been given much food for thought.

@RonBeyer Did you read the question? He's not trying to get rich here... quite the opposite.

Maybe consider survey flying for an exploration company. Travel and meet interesting people (some of whom may want to kill you).

You aren't crazy. People have started later than you and been successful. However, age does bring additional challenges, which one could argue is an ageist bias of sorts.
The first is age itself. Part 121 carriers have a mandatory retirement age of 65. That puts a hard limit on a potential airline career in terms of seniority and wages. There is no hard limit for other flying jobs, at least for domestic flying. Int'l rules are a bit tricky when you pass 60.
The second is medical. Even if you are in great health for your age, you likely have significant medical history that will need to be documented and reviewed, which can delay getting even the class 3 medical certificate you will need to solo in an airplane and take the PPL test. To fly commercially, you will need to pass a class 2 and, for the airlines, a class 1. And you have to keep passing them every 24, 12 or 6 months for as long as you want to keep flying. As we all know, health inevitably declines with age, so there is a soft limit on how long your career will last.
The third is cognitive decline. While it's not impossible to teach an old dog new tricks, it does take longer. Your training will probably take longer than someone half your age, though your glider experience should mitigate that somewhat.
There is no need for an aviation college. Some airlines still require a bachelor's degree, but they don't care what subject it is in or where it is from (as with most jobs). Other airlines may prefer one but don't require it, and non-airline jobs may not even ask.
It will be difficult to get the seniority you need to get the highest-paying airline jobs; you may well hit mandatory retirement before you reach what you consider a "decent" salary based on your previous career. Other jobs, such as charters, may have higher initial pay but less opportunity for advancement, which might be a better fit for your timeline. Others may have more flexibility, such as part-time instructing or being a ferry pilot. There are a wide variety of jobs to choose from to fit your lifestyle priorities.
Your apparent financial status, though, has one significant advantage: if you can buy your own plane to train in, you can get it done for much less money, and you can probably get it done much faster too, if you can find a CFI with enough free time. Many people who have done this even report selling the plane at a profit when they're done.

Time
All other things aside all commercial part 121 pilots have a finite end date, starting at 45 means you are going to be ~20 years behind the young guys. Since the FAA mandates retirement from part 121 operations at 65 you have 20 years left but let's look at that a bit more practically. Assuming you pay for all your own training and don't need to go the CFI route to build hours you could conceivably finish your 1500 ATP hours in a year's time if you flew full time and the weather gods were nice to you. However that's not really realistic for all kinds of reasons, weather, mechanical, practical etc. So let's say you get there in a modest 2 years. Now you're 47...
At 47 you are applying to the airlines, still need to actually pass your ATP exams, and then they need to type you into one of their aircrafts, that's simulator time and ground school time for the airline which is by no means free and takes time - this means you are getting older. They are investing in you and in their eyes they can now only get 17 years or less out of that investment unlike the young guys they may have for longer. A regional may be interested but expect long grueling days and pay on the lower side of things.
You are also starting at the bottom of the seniority tree. If you are accustomed to a nice self sufficient lifestyle now you, should not expect that working at a regional for the first few years.

There are lots of other flying jobs that are not bound by the 65 year old limit, they may be a bit more transient in nature but you can still get into a high performance airplane and be having fun. You can fly for a part 135 charter operation, be a flight instructor, tow banners, tow gliders, crop dust, fly sight seeing flights, etc. One job that I have spoken to a few professional pilots about that seems like a sweet deal is being on staff flying a corporate jet for a company, the hours tend to be decent, you end up flying some fast metal and going cool places.

An alternative to flying passenger airliners could be a cargo airline like Atlas. Might well be a better start for a career than the regionals.

Aside from the career advice (there is in fact an increasingly desperate shortage of pilots as the baby boom wave retires - you should do it if you really want it, and if you you pay attention when travelling you will spot a surprising number of starting-late 50+ copilots on the Regionals), the biggest challenge is something that surprised me when I took a jet type course at 53 (it was a unique and unusual circumstance with a private operator).
Young whipper snappers learn and memorize data effortlessly, but tend to take longer to master motor skills (think about how clumsy teenagers are).  Older-timers tend to the opposite; acquiring and retaining motor skills comes more easily, but memorizing the insane volume of stuff you have to memorize in a type course comes harder.  I trained with a much younger guy on my type course - he crashed the sim on the first V1 cut (engine failure), I didn't have a problem with it.  However, I had a terrible time remembering everything though, and always felt one step behind, because a type course is 80% memorizing crap and 20% stick-and-rudder skills.
At 45 you are not really an old timer but are starting to get there and may find that absorbing information is the tougher part (already flying gliders, the stick and rudder aspect will be effortless anyway).  Even the private course these days has a mind boggling amount of information content (I did my private in the mid 70s and my ground school was a two weekend, unfortunately named "crash course" - you could never do that today).
So, be ready for that.

They still offer crash courses for the aviation theory exams for your PPL. But they now take 2 WEEKS full time rather than 2 weekends. Interesting way to spend your summer vacation, I was seriously considering it until I got my medical denied partway through training.

For the memory issue there is Anki. It is absolutely terrific for learning checklists by heart. I use it with the independent Android client.

@jwenting I hope they use a name other than "crash course". :-/

That actual name they used was "intensive ground school".  Crash course was more of an informal name you might say.  It worked if you took the exam right away after, and if you started flight training right away to start using the knowledge.  When I did my private, in 1975, we didn't do any radio nav, or hood.

@DavidRicherby yeah, they call it the "ppl brainwash".

@JohnK Yeah, "crash course" is a pretty standard term for a high-intensity course. Also commonly (mis-)used with respect to getting your driving license really quickly.

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text:
Log dual flight time and certificates which have been revoked due to enforcement action
As with the case of Martha Lunken, who had all of her pilot certificates and ratings revoked for dammed fool stunt where she intentionally flew under a bridge, The FAA does allow people to reapply for new certificates not less than a year after the revocation as an enforcement action.  That being said, is all the flight time that a pilot has previously accumulated prohibited from being used toward the new certificate?  Or does such an aviator essentially have to start from scratch and acquire all of the required aeronautical experience flight hours listed in part 61 again?

I don't know the FAA legal basis for this, so I'm not gonna post an answer, but the way the enforcement action was reported, it was almost always stated as "it will be a year before she will be able to apply again as a student". I don't believe flight time ever expires, even in the face of enforcement action, but the privileges do. So she'll presumably have to get the endorsements from CFI(I)s, and go through all the check rides,  all over again, but will probably be able to use her existing flight time towards it.

Can Ms. Lunken log the time she was under the bridge?

Yes, flight time from before the revocation still counts. This is from Order 2150.3C - FAA Compliance and Enforcement Program:

A person whose certificate has been revoked may be issued a new
certificate provided that the person meets the qualification
requirements for the new certificate. To be issued an airman
certificate following revocation, an individual must retake all tests,
whether written, oral, or practical. Any experience requirements for
the new certificate may be met with experience obtained before the
revocation.


text:
Is there a published airspeed and TPA for Class B approach at San Diego International?
I live in San Diego almost directly underneath the downwind leg of the normal approach (from the north) to Lindbergh Field (KSAN).  The Class B airspace for the entire downwind and base leg areas is between 10,000 and 4,800 feet.  Every night I stand out on my back deck and watch the approaches being flown overhead.  It appears to me that the airspeeds and altitudes of these approaches are very similar and I'm curious about what they are.  Are these published anywhere or is there some accepted norm for a typical airliner approach to a sea level airport?  Although I could be mistaken, as I watch the turns from downwind to base and base to final, it appears that the altitude is held fairly constant and that final descent doesn't start until final approach. If anyone has any insights, I'd be interested to hear what they are.


text:
Is there an actual rated thrust for a Cessna 172 engine at takeoff power?
I could approximate the thrust by knowing the weight of my aircraft and timing the acceleration to takeoff speed, but I think that would be a little dangerous of me as well as only an approximation due to rolling and wind resistance as well as inaccuracies of the airspeed indicator.  I also realize the thrust would vary as airspeed increases due to changes in propeller and engine efficiency.
Nevertheless, was there every an actual rated or measured thrust for the C172?  You can use whatever year model you want, although I usually fly the C172N at 160Hp using a stock propeller.  I would also assume if there was a measurement, it would be at standard atmospheric conditions (sea level, 15C, standard 29.92 pressure).

A fixed pitch prop will develop maximum thrust somewhere between static and maximum air speed depending on its pitch. Finer pitch will give better acceleration from a standing start, more coarse will give more thrust at cruise.  People generally do not quote thrust numbers with props, charts calculating weight and weather effects on performance are far more important than "thrust".
However, if you want to know, do it the same way James Watt did, either by lifting a weight, moving a weight, or lifting AND moving a weight.  Watt knew just to take the first meter, where air drag was negligible.  For a Cessna, I would take the first 100 feet, release the brake, and hold a stop watch.  As John K said, it should be 500-600 lbs.  F=ma.
Just keep in mind, the key to those performance charts is that weather conditions have MAJOR effects on power and prop efficiency (prop thrust), this is what you MUST be aware of before takeoff.


text:
Why is vortex state impossible in autorotation?
An article at Skybrary states that for a vortex ring state to occur:

The aircraft has to be in powered flight. If the engines are not producing power, the aircraft is in autorotation and the upflow of air (rather than engine power) is being used to drive the rotor motion. It is not possible to enter the vortex ring state whilst the helicopter is in autorotation. [emphasis mine]

The FAA Rotorcraft Flying Handbook.pdf lists autorotation as a method of getting out of VRS.

In a fully developed vortex ring state, the only recovery may be to enter autorotation to break the vortex ring state.

Why is a VRS impossible during autorotation?

I would guess because the air is moving up, rotating the blades, instead of the blades rotating, and moving the air down. Air has to be flowing down through the rotor for VRS, yes?

For the two word answer: blade pitch.  For the six word answer: blade pitch and lack of thrust.

OK -- first, a quick review of what vortex ring state is.  I'll be brief, but there's more detail over here: What is "settling with power" and how does it differ from vortex ring state?
Vortex ring state (VRS) occurs when the rotor's shed vortices begin to recirculate into the rotor system, effectively stalling out the rotor and significantly decreasing the total thrust produced.  It is one of 4 working states of the rotor, 3 of which are described in the picture below (note: descent rates are approximate.  What really matters is the ratio of the velocity induced by the rotor to the helicopter's descent speed).  The propeller working state is the normal working state of a helicopter.  VRS is the second state shown, where descent rates are relatively low (and forward flight speed is typically very low/zero), and the windmill-brake state is what you'd see in autorotation.

In the following plot (from Leishman's Principles of Helicopter Aerodynamics), these working states are superimposed on a graph of climb velocity and induced velocity at the rotor disk.  In short, VRS occurs when you're not descending fast enough to let the downwash be blown upward and you're still trying to produce thrust.  One example would be a helicopter attempting to hover above its hover ceiling (so, even at max power, it cannot maintain altitude and has a small, negative climb velocity ratio if referenced to the below plot).  As a result, it begins to descend at an increasing speed (and, by corollary, it is falling "into" its own downwash as its downward speed increases).

So why is autorotation a way out?  Autorotation is what happens when, in a sense, you stop trying to hold yourself up.  In autorotation, the thrust produced by the rotor is minimal (depending on how you do your bookkeeping of forces acting on the aircraft) during descent.  As a consequence, the aircraft is descending so quickly that the rotor wake is actually above the helicopter!  Also, while the rotor is producing some lift, and hence some downwash, the induced velocity of the downwash in the vertical direction is very small compared to the velocity of the relative wind going through the rotor disc (in the opposite direction of the downwash).
Putting this all together in different words: vortex ring state is sustained by the pilot trying to keep pouring power into the rotor system while descending into his or her own downwash (without changing forward flight speed or tail rotor thrust, as mentioned in this neat article: http://www.rotorandwing.com/2015/09/01/flying-through-the-vortex/).  He or she is producing downwash by producing thrust, and, as the descent speeds more or less balance with the downwash velocity, the same aerodynamic forces that produce the thrust end up recirculating the downwash through the rotor.
To go into autorotation, the pilot drops collective and throttle to zero and lets the aircraft fall (more or less -- it's a little more nuanced, but that's a separate question), which, in turn, drops the induced velocity of the downwash such that it is much smaller than the vertical speed of the aircraft, allowing the vortices move with the relative wind away from the rotor (upwards) as the rotor enters the windmill-brake state.  Since there is no mechanism to hold the vortices close to the rotor (or produce them in the first place), the vortices cannot recirculate and induce VRS.

Out of curiosity, what is the 4th working state?

It's a transition between VRS and windmill brake state.  Leishman (author of Principles of Helicopter Aerodynamics) calls it "turbulent wake state".  I've updated the answer with a plot showing where it occurs.

Good answer. For lift production, in windmilling state the rotor does produce proper lift even though none of the wake is accelerated downwards. The lift does impart a downward impulse on the airstream, it's just that the total incoming airstream has a much higher upward velocity.

Agreed -- I was trying to briefly run over that by saying "almost" zero since the lift produced is relatively small compared to the weight of the aircraft, but you're right...for completeness, that nuance should be included explicitly.

A key attribute of the vortex ring state is when in it, some of the air is flowing up through the rotor disk and some is flowing down. In autorotation all flow is up through the disk, so you can't simultaneously be in a state of autorotation and VRS.


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Why does the Piper Malibu require a type rating?
The Wikipedia page on type ratings says that most single-engine piston aircraft are covered under a single class rating but under JAA regulations the Piper Malibu requires its own type rating. (I'm unsure as to whether these regulations still apply or if the JAA even still exists.)
What is different about the Malibu that would require its own type rating? And do other regulatory agencies (FAA, EASA) require this?

The JAA "still exists", but a lot of its functions have been subsumed by EASA within the EU...

The FAA does not require a type rating for the PA-46, though a high altitude training and logbook endorsement is required for the PA-46T

Here in the US the FAA can impose a type rating on any aircraft it likes (see part 3 below). Generally speaking type ratings are either for big planes or planes that may require additional training for safety reasons.
You can find the full regulations relating to US type ratings in the FAR under
§61.31   Type rating requirements, additional training, and authorization requirements.
but basically,

(a) Type ratings required. A person who acts as a pilot in command of any of the following aircraft must hold a type rating for that aircraft:
(1) Large aircraft (except lighter-than-air).
(2) Turbojet-powered airplanes.
(3) Other aircraft specified by the Administrator through aircraft type certificate procedures.

In specific relation to the Malibu the US FAA does not require a type rating, you can find a full list of aircraft that require a type rating here. However it should be noted that to fly Pipers M600 and M500 Malibu variants, both of which have a service ceiling over 25,000Ft you would need a High Altitude Endorsement (along with all the other endorsements for a high performance plane like that).
The JAA may require such a rating due to the pressurization system in the plane.

Aircraft such as the Piper Malibu, TBM family and the likes  can only be flown under EASA rules (that superseded JAA ten years ago) with an endorsement named High Performance Aircraft. No need for a type rating.
This endorsement also covers EFIS, variable pitch, retractable undercarriage endorsements.


text:
What does the crosshatching mean on this VOR-DME?
I noticed that the frequency of this VOR-DME is covered by crosshatching.

The FAA chart guide says this "indicates shutdown status."

What does this mean? Is this navaid being decommissioned?

Think I answered my own question. Looks like the VOR is gone but the DME is still operational.

You're right. From FAA Aeronautical Chart User’s Guide,

NAVAIDS in a shutdown status have the frequency and channel number  crosshatched. Use of the NAVAID status “shutdown” is only used when a facility has been decommissioned but cannot be published as such because of pending airspace actions.

Image from FAA Aeronautical Chart User’s Guide, 12th Ed.
FAA is in the process of reducing the VOR based navigation network to minimum levels so as to provide only an alternate means of navigation in case of Global Navigation Satellite System (GNSS) outage. This VOR Minimum Operational Network (MON) is expected to be in place by the year 2020, which will permit non-GNSS guidance to an airport within 100 nautical miles (nm) that has an ILS or VOR approach procedure.

Why would "pending airspace actions" render the FAA unable to officially publish the VOR as being decommissioned?


text:
How well does a composite fuselage deal with lightning?
The metal fuselage of an aircraft, being highly conductive, protects occupants, interior components and fuel from the effects of lightning by conducting the electricity around them.
Some newer aircraft, such as B787 have a fuselage made entirely out of composite materials. The major portion of the 787 is made from carbon fiber plastic laminate.[1]  Although carbon fiber conducts electricity it has a higher electrical resistance.[2][3] Higher resistance means more heat generated by the material. And carbon fiber makes up only a percentage of the composite.
Has the composite material been found to have enough conductivity to deal with a direct lightning strike without damage to either the material itself or the contents of the plane? Or do designers deal with lightning strikes in some other way?

[1] Boeing 787 Systems Manual.
[2] Department of Physics
University of Illinois at Urbana-Champaign website
[3] Electrical and mechanical properties of electrically conductive polyethersulfone composites. Lin Li and D.D.L. Chung, 1991, State University of New York at Buffalo. [.pdf]

Note that higher electrical resistance mean a greater potential voltage difference across the parts of the plane. It is this higher voltage which results in higher temperatures. It could also conceivably cause the current to seek alternative, lower resistance paths through the airframe. (Such as perhaps bags of wet meat)

"It is this higher voltage which results in higher temperatures". Not the voltage, only the current. This is why electric power transmission uses very high voltage and proportionally lower current.

@mins Oh no! You've struck one of my pet peeves! Voltage and current are two sides of the same coin. Through the same load a higher voltage produces a higher current. So to say "it's the current, not the voltage" is really a misunderstanding of the physics. If a lightning bolt of 4500 volts hits and object, say a person at 1000 ohms, it will produce 4.5 amps of current. If a bot of 5500 v hits the same guy it produces 5.5 amps

@mins As a matter of fact, the lightning hitting a metal object produces a much higher current than hitting a less conductive object like composite

In case of composite materals, the usual solution adopted for lightning protection is to have a conductive layer in the structure. Basically, this provides a continuous conductive path of low resistance over the entire aircraft exterior (fuselage, for eg), with additional protection in zones where lightning is most likely to attach (for example, the radome). This is achived usually by having a thin conductive copper mesh embedded in the structure.
For example, the 787 uses two main methods to achieve lightning protection.

The fuselage has a copper mesh 'baked' into it.
Some of the extremeties have metal foils in it to protect against lightning strike.

The composite layup uses an expanded metal foil (EMF) in its structure to provide lightning strike protection (LSP). The EMF is usually placed above the CFRP layer, as shown below. The EMF is usually a thin, lightweight metal foil embedded in the outer laminate of the CFRP or in the surface film in some cases.

The composite structure layup shown at left consists of an expanded metal foil layer shown at right. This figure is a screenshot from the COMSOL Multiphysics® software model featured in this blog post. Copyright © Boeing. Imge from comsol.com
787 also uses metal foils in some extremties (wings, nacelles etc.). From 787 Systems review:

Wing fuel tank skin surfaces— electromagnetic effects protection. Fasteners with dielectric tops (sealant flush to the outer surface of the fuel tank skin) in combination with copper foil protect against external ignition sources such as lightning and electrostatics on the wing tank skin
  surface by diverting and distributing current.

The metal mesh is the usual method in practice at present and used in other places too, like helicopter rotor blades and fuselage. However, work is going on for using other methods like conductive composites, conductive surface layers etc.


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How are crews managed after a diversion (far from hub)?
While reading one of the reports of flight diversion, I started thinking about how airlines manage aftermath of the diversion especially for long haul transatlantic flights.
Many of the reports say airlines provides a replacement plane. Replacement plane flies to the diversion airport, load up the passengers and continue.
If the original flight is full, what happens to original crew? Working with the assumption that new flight has new flight/cabin crew and there is not enough place for all.
If the airport is at significant distance where the replacement comes from or still has to fly significant distance, it's possible that replacement flight crew might run out of flying time.
Do they provide multiple sets of crews - one to fly to diversion and one to fly to actual destination.

This is actually a really good question. I've been a pax on transatlantic flights that have been diverted to places like Gander, Canada (pray you're never diverted there...) because of things like an elderly passenger dying mid-flight. My hunch would be that the crew flying the replacement bird would also be in charge of taking the pax to the original final destination.

@JuanJimenez It would depend on where the planes have come from and are going. In the case a US-Europe flight being diverted to Gander, if the replacement plane comes from Europe, the crew won't be able to fly Europe-Gander-Europe in a single shift, and I doubt the airline would want another plane sitting on the tarmac for a day while the crew rested.

I'd say you've answered your question yourself, by listing the various scenario's, any or all of which could be of concern in a particular situation. Handling a diverted flight is a juggle between, safety, time, comfort factor (for crew, for passengers), cost, etc. In turn these are affected by feasibility, location of base (for replacement of crew/airplane), ease of availability of replacements, number of passengers, break up of their final destinations (likely factor when flying to long-haul to a hub), fuel and tech facilities available at the diversionary airfield, whether local 'diversion handling' contracts are in place, or the situation is being handled on-the-fly at an obscure airport. Airlines tend to have their own tailor-made SOPs, or guides.
These issues are ideal ones to be addressed by Airline Alliances such as STAR or 'One World' and traditionally all help is given to such flights. "You today, could be me tomorrow"
Assuming the airplane is ok, The change of crew may not be required if the remainder of the flight fits within the DTL's (Duty Time Limits) and the extra landing for recovery falls within the ambit of the rules. Crew are expected to be rested enough, when reporting for Flight Duty, to operate to their limiting DTL's. There are allowable extensions to these limits too, provided every crew member is upto it, ie not fatigued, and the Captain judges it to be a true reflection of the situation. The Captain would have to document all this in the Regulatory/Company paperwork. Note that Long-haul flights carry more crew than the minimum for shorter flights, so all crew get some time-out and an opportunity for horizontal rest, ideally in the form of a 180deg reclinable seat or bunks, normally in a private crew rest area.
For Ultra Long Haul flights, the hours, and crew numbers are ideally decided on a case by case, 'city-pair' basis, along with the Regulator and related procedures documented by the Operator, acceptable to crew, and approved by the Regulator.
In case a layover has to be declared by the Captain, many Operators/Regulators have a concept of Minimum Rest, which maybe typically 8 or 6 hrs of undisturbed rest, sometimes called (hotel) "key to key" time. This may provide more certainty than organizing a relief airplane that has to fly 12 hours to get there.

Ferry flights are actually very common and typically only have the 2 or 3 pilots as total people onboard. Cabin crew are only needed with passengers and their duty time restrictions are different from the pilots. However with a full new cabin crew (maximum of 50 passengers per flight attendant, minimum 2 attendants for typical airline flights in the USA) there are a few extra jump seats, or the company could simply arrange for a slightly larger plane.(or use two smaller planes.)
Failing all that, the company can purchase a few tickets on another airline for the extra crew. Legally in the USA airlines have a few contractual obligation to passengers and this results in airlines occasionally purchasing tickets for customers to fly on a competing airline when sold out flights are replaced with a smaller plane.
It would be unlikely to send a replacement from a long distance, this would be a needless waste of fuel and crew time. If they could not open up one of their own fleet in the local area then the company would hire a charter plane that is local. They may also just wait until another regular flight will be in the area depending on schedule frequency.

Hmmm... very common? That's very ambiguous.

Ferry flight are a daily occurrence. Most new aircraft are transferred and delivered as ferry flights. As are any aircraft at the hour limits for inspections or those in need of repair so that they may get to the location of the inspection or repair.

Of course, but I was thinkin' compared to operative flights: not so common. As such, probably hundreds of ferry flights in the air at any given moment, thats for sure.

Any of those combinations, and some others can happen. The dispatcher will try to find cheapest way to handle the diversion that fits all applicable regulations and safety rules, and since the options they have available differ from diversion to diversion, the solution will probably be different every time as well.

If the crew that files in the replacement aircraft has enough duty time left, they are the obvious choice to continue with it. It does not have to be though and occasionally the dispatcher will come up with some other combination.

If it took enough time to fly in the replacement aircraft that the original crew is now rested and can legally start a new shift, and they are rated for the replacement aircraft, they can also operate the continuation. Sometimes the continuation will even be delayed by a couple of hours to allow this instead of needing another crew.

The aircraft can carry a second crew to operate the continuation. The cabin crew also probably isn't needed for the ferry flight, so they only start duty when they board the passengers.

Additional crew can arrive as passengers on any other, completely unrelated flight, likely of a different operator. Any crew members no longer needed at the point of diversion can leave the same way.

Even if replacement aircraft is provided to complete the flight, the agents may rebook some passengers to other flights (of other operators) when it gets them to their final destinations faster. That can free up some space in the replacement aircraft for the now off duty crew.

Some flight crew needs to stay around to ferry the diverted aircraft back home once the mechanics get into good enough shape that it can be flown. The cabin crew might be able to return with them if there was no other option and the state of the aircraft allows it (unless the aircraft gets ferry permit only allowing essential crew). The same goes for the mechanics that might have arrived on the replacement to carry out the repairs.

The dispatcher will consider the available combinations, estimate their cost—which includes indirect costs; the replacement aircraft was probably scheduled for some other flight, so that will now have to be rescheduled too and some passengers will have to be rebooked there, or entitled for a refund etc.—and pick what looks best.


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Would a refueling stop be cheaper than finding lodging for all the passengers?
This is somewhat late followup question to my original question. Basic story was flight got delayed by almost 24 hours because first, technical reasons, secondly temperatures were very high.
As far as I can see airlines had to accommodate all the passengers somehow, either in terms of hotel rooms and meal or on other flights. There are costs involved in every action.
If they had taken off Abu Dhabi on less fuel and then refilled somewhere else would it have been cheaper? Would such refueling stop be allowed where passengers are not allowed to get off? Just fill her up and continue.
Without knowing any technical/legal/contractual details, my simplistic view is, you land at some airport around 6 hours away, fill up your tanks - might take around 1 hour and continue rest of your 14 hours flight. Your crew could be in time limits as they must be provisioning for full length of the flight plus possible diversions, moreover almost working as planned and you don't have to pay for hundreds of rooms and/or rebooking/re-routing costs of the passengers.

Original flight was non stop, but what I am trying to find out if such detour would have been worthwhile than making alternative arrangements for all the passengers

Related: What criteria make an airport suitable for a technical stop for a large airliner?

If it would've been worthwhile, the airline would've done it.   They aren't in the business of losing money.  Because they didn't do it, it is easy to conclude that it wasn't worthwhile.

Way cheaper to cancel the flight and tell everyone to come back the next day and offer a voucher of some sort as compensation for their troubles.  The only people that will have to be put up in hotels will be connecting flight passengers.  Pretty much all the pax that live in the area will just go home for the night.

Agreeing to your logic. Practically, based on general observation and not based on the any statistical numbers, many of these flights have 80% or more connecting people coming from India/Pakistan and many other Asian countries.  So costs of accommodating people could be high


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In a helicopter does forward flight produce a rolling moment?
In forward flight the advancing blade will produce more lift than the retreating blade. It seems this would produce a rolling moment. If so, does the pilot have to move the cyclic to compensate for this? If it doesn't, why not?

Yes, forward flight tilts the rotor sideways, which does produce a rolling moment about the Centre of Gravity.
From J. Gordon Leishman, Principles of Helicopter Aerodynamics:

The picture shows the lateral tilt from longitudinal airspeed, which must be compensated for by tilting the swash plate. If the CoG is underneath the rotor axis. the rotor thrust vector $T_{MR}$ must point vertically upwards in order to stop the helicopter from rolling. Part of the rotor trim considerations.

Picture above shows the lateral stick setting as function of airspeed for an example helicopter, which resembles the UH-60. Note that below 70 its, there is negligible lateral stick trim input required.

Yes cyclic is used to compensate.
The advancing blade is allowed to "flap" up to compensate for its extra lift, and the retreating blade flaps down to compensate for its decreasing lift.  On an articulated rotor, each blade has a flapping hinge for this purpose.  On a two blade teetering rotor, the blades being on the same axis are flapping up and down in harmony and the teetering pivot at the center takes care of it.
If the cyclic was perfectly centered (swash plate horizontal) the rotor disc would be flying a long with a slight tilt away from the advancing side as the machine flies straight.  But this would impart a lateral moment that would make the machine turn to the left as it flies forward.  So to compensate the pilot is initially applying a small amount of compensating right cyclic without thinking about it (on a machine where the right side advances), so effectively the advancing blade gets a slight reduction in pitch and the retreating blade gets a slight increase in pitch, becoming more and more the faster you go.
As you get faster and faster, either the retreating blade runs out of pitch authority or wants to stall as its relative speed gets too low, or the advancing blade's tip becomes trans-sonic. One or the other.  This is what limits helicopter speeds.


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Does the other engine have to go through extra checks when one engine fails
Many times I read articles on sites like aviaton herald about engine shutdown in fight because of some problem. It's given the problematic engine will be repaired.
Question is about other working engine. For a twin engine jet, for a period of time, it did double work. After landing, does the engine go through some extra inspection and/or maintenance routine because it went through extra responsibility.
I tried using word extra load as I really don't know if engine has any extra load. All I know is aircrafts are designed to operate/land safely even if one engine fails.

If the engine might have failed because of poor or neglected maintenance procedures, wouldn't it be prudent to check the other one?

A long time ago I knew an amateur pilot who gave me this piece of wisdom: the purpose of the second engine in a twin engine plane is to get you to the scene of the crash.

"Double work": no.

@MarkRansom But that is for small propeller-driven aircraft. Large air transport planes must have stronger engines and often even be ETOPS capable.

In an engine-out scenario, the remaining engine(s) are operated at a higher power. In itself, this does not require additional checks, just like if the crew was required to make a max-power takeoff versus a lower one.
However, this additional stress may push the remaining engines over operating limits which requires maintenance action. The most typical sign would be engine exhaust gas temperature (EGT) over limits. Typically as an engine ages and it becomes less efficient, it requires more fuel and moves less air, increasing EGT. High EGT is a reliable indicator of wear, and obviously can cause damage itself, e.g. melted parts. The two regimes where engines first hit EGT limits are operation at high powers, and starting.
If an EGT exceedance occurs, this is logged by the avionics and mechanics will action a procedure. Depending on the magnitude (degrees and time), this may mean no action but watching the engine, a borescope inspection, or taking the engine off the wing for overhaul.
Other common exceedances are overthrusting/overboosting, when the primary thrust setting parameter exceeds limits (N1 rotor overspeed, EPR too high). This is rare in modern computer-controlled FADEC engines, as the control loops manage this well, but occurs in older engines. Excess vibration also is a sign of damage, pointing to some physical change internally.

Just as an integration to the other answers.

Aircraft's engines possess indeed several power ratings.
The value that is normally found on the price tag is the so-called Maximum Continuous Power MCP i.e. the maximum power that the engine can output for prolonged periods of time.
Alongside this value there's for example the Maximum Take-off Power MTP, which is a power level that can be held for no more than 5 min at sea level. In extreme cases the engine can be pushed to its Transient Power which can be held for no more than 20 sec (the actual value depends on the manufacturer).
Should any of these limitations be overcome, an extraordinary maintenance/overhaul is necessary, which might even end up with the engine being scrapped.

authors: Vladimir F Героям слава


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Left hand seat, is it so important?
With reference to this article on aviation herald at Accident: Shanghai B738 at Shanghai on Jan 3rd 2020, tail strike on landing, captain and first officer swapped seats in flight where the report discusses swapping seats between captain and first officer. I'm trying to figure out why so much weight was given to swapping the seats - except may be bad timing.
As a person who is not affiliated with aviation, I am curious to know apart from responsibilities and prestige that goes with the position, are there any differences between flying from right hand side vs left hand side. Does captain side has more controls available?
If someone gets incapacitated for whatever reasons, how is it managed?
Additional question - as pilots move up the career, do they have to learn few skills again like controls they used to perform with left hand vs right hand as they swap the seat.

We have two closely related questions already: here, here. Do either of them help?

@Pondlife, first one helps a little, but did not show up in my searches. Second one does not at all as it does not discuss the importance of swapping the seats

For swapping we have this question that might be relevant.

One difference comes to mind: I think recently there was an answer which stated that the backup batteries of some aircraft only power instruments on one side.

Maybe it is about the (un)safety of switching seats while in flight: without a relief pilot, that leaves no-one at the controls for a while.

There should not be any great differentiator between left and right seats. The American Airlines Training Center FFS (simulator) for the B737 has the nose wheel tiller only on the left side. The actual aircraft should be set up identically to the simulator. Other than that, most pilots at the ATP and airline levels should be comfortable in either seat.
In larger and/or turbine powered aircraft (as well as the majority of glass cockpit aircraft), the instrumentation is duplicated on both sides of the aircraft. You both have the same information. But, there is only one set of controls for some things like the throttle quadrant, autopilot, and radios located in the center of the panel, overhead, or on the central pedestal between the pilots. It’s like an American (me) driving a fifteen passenger, stick-shift van around London for the first time. Driving and even shifting are simple procedures. It is even simple to remember in which lane to stay when turning corners. But, your entire ingrained site picture is off. And which hand does what is reversed. Simple to overcome with experience and practice.
With low time pilots, on the other hand, there is quite a difference. Most pilots get most of their first 200-500 hours flying left seat only. Most six-pack steam gauge training aircraft have their instruments oriented toward the left-seat pilot. Making the transition to right seat can be a challenge at first. But, this challenge can be easily overcome with practice. Think of it this way, try playing a musical instrument or a sport with opposite hand orientation from the way you first learned it. Try even to tie a tie or your shoe laces opposite your normal routine. It is not impossible. It becomes a non-issue with some practice. I still find it daunting to land from the right seat even though I can perform most other maneuvers somewhat fine although with more thought.
By the time a pilot reaches the CFI level, they should be more than comfortable in the right seat. Most of their flying from the start of their CFI training on will be from the right seat including the checkride. Some CFIs will even fly solo from the right seat out of habit. Especially in aircraft that only have a right door.
As far as pilot incapacitation, with only limited experience in the B737 sim, I can’t think of much you can do from one seat that you can not do from the other. Operation of the nose wheel tiller and certain circuit breakers come to mind. I think the cabin pressure controls would be a stretch from the captain’s left seat position depending on their reach. It would still be a good idea to remove the incapacitated pilot from their seat if able. Just to make sure that they do not accidentally get in the way of the controls. It would also be of great aid to have someone coherent in the vacated seat to help with the radios. Even if they are not a pilot.

Your answer is contradictory, first you say pilots should be comfortable in either seat, but then your last paragraph says the opposite.

@GdD - If I changed the order of the paragraphs, would that make it more understandable? As a right-hander, sparring south-paw was no big deal. Playing golf with my father’s (also a rightie) left-handed clubs is still darn near impossible. Yet I still catch and throw with proficiency only with one hand. Not an issue for football. Not great for baseball. While natural ability counts for a lot. Experience and practice counts for more. Like playing piano chords on one hand and a complex melody with the other. Then, reverse hands. Simple with practice , experience, and a little extra thought.

I think getting rid of the first paragraph would fix it @DeanF.

I've heard of cases where some component on the captain's side malfunctions - a screen burns out or a gauge stops working.  And rather than rely on constantly looking over at the first officer's instruments or asking them for readings, or asking the first officer to take over the remainder of the flight, it might make sense for them to switch seats.

@DarrelHoffman - I get what you are trying to say. Since the FO makes half of the takeoffs, cruise flight, and landings anyway, what besides ego would keep the captain from giving the FO control of the aircraft? Aside from an incapacitated pilot, there is no reason for both pilots to be out of their seats at the same time in flight. Besides, pilots train for partial panel flight. Both pilots should be able to easily see their backup instruments.

While the student pilot will be flying the small aircraft during initial training from the left seat, their type rating for the multi-crew aircraft and at least the first year of line flying on it will be purely from the right seat.

Switching the role of each hand when playing piano may take some practice, but at least both hands are already doing the same type of movement, and most skilled pianists would be close to equally dextrous with both hands - even beginners may be if they play mainly classical music Switching from right- to left-handed guitar, on the other hand (ha!), is very, very difficult for most people.

The specific issue in that event, where the FO landed hard, is related to the sight picture outside from the seat.  If you are used to the sight picture from the right side (mostly the general orientation and angles of the windshield frame to the outside view, and the lateral location of the runway relative to your sight line) and switch to the other side, where interior edges in your view slopes the opposite way and your sight line is now on the opposite side of the runway centerline, it can throw your visual judgement off and you end up flaring high, or late.  Some pilots are more affected by this than others.
New flight instructors in light aircraft go through this phenomenon when they start their initial training, which starts off with a checkout flying the trainer from the right seat.  Watch a new instructor on training at the airport doing his first circuits/patterns from the right side, and, with some new instructors, it looks like a brand new student trying to learn to land from scratch.
The reversed controls may be a factor, but only insofar as the wheel is in your left and instead of the right and I don't think most pilots have much problem swapping hands to land the airplane.  Other parts of the cockpit being reversed aren't really a big deal here because we are really only concerned with the flare to land, not working switches.
When you are with an airline and you do recurrent sim, even if you are a right seat only FO, you often fly both sides during recurrent training. On a 4 hour sim session, if it's two FOs training together, they will swap sides half way through so each does half the session in the left seat. So most FOs have some experience working from the left side in the sim. But when you are confronted with the real deal in a 3-dimensional world, some pilots can still be thrown off and misjudge the flare the first couple of times.

The pressure of doing something "for real" the first time instead of "for practice" will throw many people off, even if they're not doing anything different than what they've practiced, no matter the thing they're doing. The first time I drove down country roads to my girlfriend's house was terrifying! It felt like I was driving a 30 foot wide car down a 3 foot wide road, even though I'd been driving for a couple of years by then, and had ridden with her in the very same car down the very same roads.

Most airplanes have a side by side pilot configuration, with throttles, flaps, gear, autopilot and other very important controls located in a central console. A pilot who flies in the left hand seat gets used to having the stick in the left hand and manipulating the throttle and other controls with their right, the right hand pilot vice-versa. Pilots are trained for one position or the other, and become familiar with the controls in their particular positions, and learn to work as a team in that position. The goal is to have reactions become automatic and smooth.
When pilots switch seats everything is reversed, actions are no longer automatic. Controls are no longer where they are supposed to be, using them feels unfamiliar. This damages efficiency and can reduce safety, which is why it was an issue in that case.
If a pilot becomes incapacitated the remaining pilot is supposed to remain in the seat they are accustomed to rather than changing positions.
When a pilot moves from first officer to captain they have to be retrained to use the correct hand for everything.


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Airplane generations - how does it work?
I was reading about Atlas B763 that was involved in an accident on Feb 23rd, 2019. Based on what I read plane was 25 years or so old.
As a person who has no relationship about aviation industry except occasional flying as a passenger, I'm curious to find out if these planes also have generations or models like car manufacturers do e.g. Honda civic, 2015, 2016 or 2017 models where there are small but distinct changes.
Based on Wikipedia pictures, cockpit photos are different for various generations as technology is improving/changing.
Are pilots rated on particular generation of the plane or once you are rated on B763, you can fly any one of them whether it was built 25 years back or yesterday?

While airliners don't have "model years" like cars do, they are certainly changed over time.
There are major "generations" of some aircraft types, like the 737. The "original" (-100,-200) was replaced by the "Classic" (-300,-400,-500) which was replaced by the "Next Generation" (-600,-700,-800,-900) and most recently replaced by the "MAX" (-7,-8,-9,-10). While technically still the same aircraft type, there can be major differences between them, especially from the pilot's perspective.
The 767 hasn't had any major "generations," but it has had multiple models, as is common with airliners. These are mostly just adjustments to fuselage length, fuel tanks, and structures. Other than small changes to systems, or different guidance to prevent a longer fuselage from stiking the ground on takeoff or landing, there is minimal training required. The 767 cockpit was even designed to be common with the 757 to minimize required training.
The FAA requires pilots to get a specific "type rating" to fly any aircraft over 12,500 lb max takeoff weight. The scope of this rating is negotiated between the manufacturer and regulator like the FAA. This could change with new versions, as with the 747-400, or even be common, as with the 757 and 767. There may also be training for each minor model, though not as in-depth as a new type certificate.
There are also changes made within the minor models over time. The biggest changes would probably be things such as modifying the winglets or adjusting the engine installation to get better performance, or a new cabin interior design. There are also many smaller changes that occur throughout the airplane. There isn't really a regular schedule for these like in the car industry, as there's less turnover in the aircraft market and major changes can be very expensive to certify. There would have to be a significant benefit to make a change requiring new pilot training, which is why those changes tend to happen in the more major "generations."

For engines, the trend towards a "package deal" for leasing and maintenance instead of  purchase means that the engine specifications are often "tuned" to the requirements of a particular airline or even particular routes being flown. With electronic control systems this does not mean changing mechanical parts - think of it as similar to remapping a car engine for the minimum "cost of ownership" (fuel + servicing) for the specific driving conditions in which it will be used.

So basically the manufacturer of an aircraft documents in detail how similar it is to their other aircraft and how much training (in the opinion of said manufacturer) is required to transition when an update to the model is made, whether minor or major?

Pilots will have a "Type Certification" that ensures they have been trained and can operate a specific model, or group of models that have identical cockpits. The classic example is the 757/767, the 757 being a narrow-body and smaller plane, but both have the same cockpit layout, so a pilot can go from one to another without issue.
This FAA Document (PDF) lists the type ratings for each aircraft. You can see that the 757 and 767 share a type, as do the A318/319/320/321.


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What is this item on the nosewheel of the Sukhoi PAK-FA?
I noticed a small item on the rear side of the nose wheel in multiple images of the Sukhoi PAK-FA, shown below.  The item in question appears to be a grille wrapping around the back of the tires and I cannot think of any reason to put something like this on an aircraft's landing gear.  Does anyone know what function it serves?

Image credit Dmitry Zherdin.  Obtained via Wikimedia Commons.

Image credit Alex Beltyukov.  Obtained via Wikimedia Commons.

Pretty sure its a debris deflector, so that the aircraft doesn't throw up things into the intakes.

@RonBeyer Interesting, do other Russian fighters have them as well? I understand the Russian practice is to build aircraft to withstand the battlefield and FOD at the airfield, but had never noticed one of these before.

I'm not sure about Russian fighters, but it is pretty common on a lot of different aircraft.

"Especially design for rough field operations the single wheel sturdy nose gear features a mud guard/ FOD screen with downward facing deflectors louvers guiding all debris away from the large air intakes. It pivots around the wheel axis and is connected to the nose gear leg by two struts." Source. @RonBeyer is right.

Looks like he forgot to feed the meter and the parking police booted it!

It is a mud guard/FOD deflector, which is found in almost all Russian combat aircraft operating from land bases.
This is basically a reflection of the Russian philosophy of aircraft operations:

The fact is that most Russian fighters and attack aircraft were built to operate in pretty horrific conditions, ones that would chew up and destroy their western counterparts. Features that allowed them to do this usually included twin tire nose gear and a mud and debris catcher located behind the nose wheels.

The nose debris deflector prevents debris being ingested by the air intakes (which are to the rear of nose wheel) and damage to the airframe. According to ausairpower.net, it also has:

Alternate intakes for the propulsion system, as seen on earlier Flankers.

for rough field operations, similar to Mi-29. The image below shows the add-ons.

Detail of inlet and lower fuselage area (Sukhoi); image from ausairpower.net
The FOD deflector is similar to that of the Su-27's, as shown below:

Su-27 nose landing gear, from another answer; originally from maybach300c.blogspot.com

This sounds like a very cheap and easy solution. Why would American jets not implement this also?

@DavidGrinberg It goes back to core philosophy. American fighters are designed to operate from generally well-cared, paved runways and bases... so there's an assumption that most of the time the American fighters would have relatively ideal conditions. The Russians take the opposite approach and design for horrible conditions, expecting their fighters to operate from country roads, unpaved impromptu runways, fields, basically anywhere anytime. Which is better? Well that depends on your projected operating conditions...

@SnakeDoc right, but it seems like that extra piece on the wheel is a very small price to pay such that you can get the best of both worlds

@DavidGrinberg Russian fighters have a lot more than just the wheel FOD deflector that enables them to operate in rough conditions. They have deflectors covering intakes to prevent FOD ingestion, don't hang ordnance as low on the body as American fighters (risk of damage or strike FOD on runway at takeoff/landing), size and shape of the aircraft, weight, dual nosegear wheels/tires in some cases, etc. So, it's the entire design philosophy that enables Russian fighters to operate in the conditions they are designed for. American fighters simply are not designed with the same environment in mind.

It's basically a mud deflector.  Prevents or reduces rocks, mud, or other FOD that the nose wheel kicks up from getting airborne and either smashing into the airframe or being ingested by the engine.  You will notice that most Russian fighters have this feature on the nose landing gear per their philosophy of war and the substandard conditions found at Russian airbases.


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What is the purpose of those casing treatments and how were they designed?

The images show a kind of casing treatment used in Russian aero-engines.
From what I have found out the first engine featuring this kind of casing treatment was the Tumansky R-13. Since then it was used in numerous Russian jet-engines (e.g. Tumansky R-29 or Klimov RD-33).

Casing treatments are usually used to increase the operating range of compressors. And there exists a wide range of different types/geometries of casing treatments:

I was not able to find any documentation or publication on the working principle of the Russian casing treatments and how they were designed. Since they were designed in the 1950s their design was likely done by correlations. The interesting thing is that the design of the 1970s looks very comparable so the advances in 1. computing power and 2. operating experience did not change them.
Does anyone have information on:

The design rules for these casing treatments (stagger angle, skew angle, axial position)?
The working principle or intent (recirculation, blowing, sucking)?

I figured when NASA calls it a »casing treatment« it might be the term to describe it. I might be mistaken though. (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770025210.pdf)

The casing treatments shown work by providing an alternative path for the rotor tip leakage flows; which otherwise collect at the rotor tip when highly loaded and block the flow resulting in a surge.
The lack of change is because there was no significant improvement in computing power between the 50s and the 70s that would help with such designs, (in fact it is only very recently that the flows can be accurately modelled.) and the cost of the experiments required to substantially iterate the design would be prohibitive.
The difference in designs is partially driven by parallel development, partially by patent avoidance, and partially the desire to minimise the impact on the compressor's components and its efficiency.


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Is there an alternative (more robust) operating law/setting for jet-engines? After one engine failed?
Sorry for the complicated Question.
I was wondering (after reading this report) if a two-engine air plane has an alternative operating scheme/setting for the remaining engine. Maybe a setting which is not that fuel efficient but more stable with respect to compressor surge and stall.
In the cited report one engine suffered compressor stall (maybe by bird-strike) and was subsequently shut down. The other engine was reported to have left a trail.

Aircrews regularly practice emergency procedures for engine out scenarios in their training and simulations.
Aircraft manufacturers and airlines provide procedural outlines for various possible emergency conditions specific to the type of aircraft.
During an in flight emergency, fuel efficiency is not a priority. The aircrew is to ensure safe flight of the aircraft and the priority becomes landing quickly and safely. This may require use of the engine in any fashion to keep the aircraft in flight.
In the report you reference, there is no real way to know what (if anything) caused what appeared to be a trail of smoke seen by another person in another aircraft waiting to take off.

Maybe my question was not precisely enough worded. My question was only triggered by the report and meant a lot more general. I was wondering if there exists a switch in the cockpit which alters the control law of the engine.

Not sure what you mean by "control law", but flight controls and the throttle to the remaining engine is the key to stabilizing flight after failure of the other engine.

I was thing of an alternate FADEC control law

authors: Азиз Абдуллаев


text:
What US airports have approaches with LAAS?
LAAS (Local Area Augmentation System) is a ground-based GPS augmentation system, intended to be placed at airports to get position accuracy down to around 3m (~10ft) from WAAS's 10m.
I've read that it has been installed at a few airports, but can't track them down; I've also heard, anecdotally, that installation has ceased as WAAS is more than sufficient.
Is LAAS still being installed, and if so, where can one fly a LAAS approach?

The Local Area Augmentation System was the FAA term for the Ground Based Augmentation System (GBAS), which is an International Civil Aviation Organization (ICAO) standardized system for local area differential systems.
The FAA has migrated to the ICAO term GBAS, though Several historical FAA documents still retain the LAAS terminology.
According to the FAA GBAS FAQ page,

Currently, two U.S. locations have obtained operational approval for public GBAS use and support revenue airline traffic. These stations are located at Newark Liberty International Airport (EWR) and Houston George Bush Intercontinental Airport (IAH).

According to FAA, development of GBAS continues and,

The FAA and other States are in the process of validating proposed ICAO GBAS standards to support Category III (CAT-III) precision approach operations. The FAA expects ICAO will approve GAST-D Standards and Recommended Practices in 2015

Also,

The FAA continues to validate the GBAS CAT-III requirements as part of the Next Generation Air Transportation System (commonly known as NextGen). The FAA has currently deferred any Federal acquisition decision on GBAS.

Also, though GBAS and WAAS are mutually exclusive at present, some future aircraft like A350 are expected to support both GBAS and WAAS.

You might want to add that the FAA's abbreviation for GBAS approaches is GLS (cf. ILS) and that's what you see on approach plates for the two airports you mentioned.


text:
Where can I look up FAA Letters to Airmen?
I was recently asked if an airport was covered by a Letter to Airmen (LTA) providing IFR separation for VFR practice approaches, and I realized I had no idea. How can I look up LTAs for an airport, and do they ever expire?

They are searchable at FNS NOTAM search: https://notams.aim.faa.gov/notamSearch/
A link is provided to a PDF, containing a link to the actual LTA.
(Filter by LTA, remember the agreement might not be with the airport, but with the ATSU, like the local TRACON/ARTCC, try searching by airport name + radius).
Expiry date is shown in the details view.

Importantly, to actually read the letter, you need to click on the camouflaged "PDF" link at the top, then follow the link in the download to the main LTA document. Not the best flow.

Not the best flow indeed :) I'll add it to the answer for completeness if you don't mind.

Of course, go for it!


text:
What are the specs for runways at international airports?
1) What are the materials that international airport runways are made of? If runways consists of several layers, what are they made of, and what is their depth and other specifications?
2) What are the surface specifications/properties required of such runways?
3) What kind of routine maintenance drills do such runways require?

This may provide some information: Do runways need some special kind of tar or protective layer? (additional links included).

http://www.faa.gov/airports/engineering/construction_standards/

And for general info: https://en.wikipedia.org/wiki/Runway#Pavement

And here for the maintenance part

Runways for international airports are usually man made, which means that they are made up of asphalt or concrete and sometimes are a mixture of both. The depth for the runways are 29cm to 33cm.
Runways are usually around 150ft wide. For an international airport will have a runway around 6,000ft long, but depending on the size of the aircraft that land there a runway will need to be 8,000ft or more.
I found this link which should give you information on runway maintenance.

6,000 ft is a really short runway. Even 8,000 ft is not that long. International airports usually have runways 10,000–12,000 ft long.

33cm is about 13 inches. They've just built a new road near me and asphalt and concrete in the road are thicker than that. I'm pretty sure that a runway takes a more serious pounding than a highway - especially in the landing areas.

@JanHudec Yeah, 6,000 ft. is definitely quite short for a large passenger service airport. It's normal enough (even a bit long) for GA, but it's quite short for something that handles anything the size of a 737 or up. Orange County is a notable exception at ~5,700 ft.

@reirab It depends on what airport it is. Some international airports can only fly Q400's or smaller because there runway is so small.

@Ethan, that is why I said usually. It still does not make saying around 6,000 ft any more correct though. At least would be correct, because 12,000 is at least 6,000, but around is not, because 12,000 is not around 6,000, it is twice as much.


text:
Is there a parameter that links the areas of the fuselage and control surfaces?
Do aircraft designers look at the ratio of how much fuselage surface area can be loaded onto a given unit of wing and tail surface area including elevator, aileron, rudder etc? (Possibly, the surfaces of propellers and internal parts of jets, may be excluded while making such calculations.)
Is there such a parameter, and if so, what are the normal values?
This question is for normal fixed-wing and rotary-wing aircraft, and mostly commercial aircraft.
This question is NOT about fighter jets, space-shuttles, canard-wing designs, flying wings, lifting body and other cutting-edge-technology stuff.

If it were, the SC-7 Skyvan would never be certified. I've always been amazed that thing can make it off the ground, it's the most ungainly-looking aircraft I've ever seen, and that's in a universe where the A-10 exists.

this question has not been clarified at all. what does "ratio of how much fuselage surface area can be loaded onto a given unit of wing and tail surface area" means?

Is your question "how are control surfaces sized given a fuselage size?" if so, you might consider simplify your formulation.

I do not know a method that relates the fuselage area to empennage sizes, but there is rule that can be used to estimate the size of the vertical and horizontal tail. It is using the so called tail volume coefficient. For the horizontal tail given by:
$$ V_h = \frac{S_h \cdot l_h}{S c} $$
With $V_h$, the horizontal tail volume coefficient, $S_h$ the horizontal tail surface, $l_h$ the horizontal distance between the c.o.g. and the tail, $S$ the wing area and $c$ the average wing chord.
Basically, this coefficient says that the moment induced by the wing scales with $S$ and $c$, whereas the counteracting moment given by the tail scales with the area of the horizontal wing multiplied by the distance to the c.o.g., and that there should a certain ratio between the two.
A well behaved aircraft typically has a $V_h$ which falls in the following range $^{[1]}$
$$V_h = 0.30 ... 0.60$$

If $V_h$ is too small, the aircraft’s pitch behavior will be very
  sensitive to the CG location. It will also show poor tendency to
  resist gusts or other upsets, and generally “wander” in pitch
  attitude, making precise pitch control difficult. $^{[1]}$

We can check the values for some commercial aircraft here (I chose Airbus, but it should hold for others as well) :
$$\begin{array}{|c|c|} \hline
 \text{Model} & \text{$V_h$} \\ \hline
\text{A330-200} & 0.957 \\ \hline
\text{A330-300} & 0.791 \\ \hline
\text{A340-200} & 0.733 \\ \hline
\text{A340-300} & 0.791 \\ \hline
\text{A340-500} & 0.729 \\ \hline
\text{A340-600} & 0.729 \\ \hline
\end{array}$$
You can see that the values are already higher than given by the guideline, showing the issue of the generalization.
Another fact that causes the deviations, is the fact that the Airbus aircraft are designed in families. Thus, they design an aircraft, and then add some extra fuselage length to generate a larger family member. This will possibly drive the tail volume coefficient away from the ideal case.
For the vertical tail there is an equivalent form:
$$V_v = \frac{S_v l_v}{S b}$$
With $V_v$, the horizontal tail volume coefficient, $S_v$ the horizontal tail surface, $l_v$ the vertical distance between the c.o.g. and the tail, $S$ the wing area and $b$ the average wing span.
A well behaved aircraft typically has a $V_v$ which falls in the following range $^{[1]}$
$$V_v = 0.02 ... 0.05$$

If $V_v$ is too small, the aircraft will tend to oscillate or “wallow” in yaw as the pilot gives rudder
  or aileron inputs. This oscillation, shown in Figure 5, is called Dutch Roll, and makes precise
  directional control difficult. A Vv which is too small will also give poor rudder roll authority in an
  aircraft which uses only the rudder to turn. $^{[1]}$

Again checking the values:
$$\begin{array}{|c|c|} \hline
 \text{Model} & \text{$V_v$} \\ \hline
\text{A330-200} & 0.057 \\ \hline
\text{A330-300} & 0.059 \\ \hline
\text{A340-200} & 0.055 \\ \hline
\text{A340-300} & 0.059 \\ \hline
\text{A340-500} & 0.049 \\ \hline
\text{A340-600} & 0.049 \\ \hline
\end{array}$$
Here the values are quite close to the general guideline.
Another interesting plot is shown by This tail design page by Stanford
Here it shows that the tail volume correlates quite nicely to fuselage height and length.

Image showing correlation of aircraft vertical tail volume as a function of fuselage maximum height and length.
It should be noted that aircraft aren't really designed by these guidelines anymore, all the control surfaces are designed such that they provide the control authority necessary, not to match a general rule.
$^{[1]}$: Lab 8 Notes – Basic Aircraft Design Rules Link

When computing the vertical tail volume coefficient for a twin vertical tail, is the Sv used the total combined area of both fins, or just one?

I would use the combined $S_v$, otherwise it just as good as a single vertical tail of the same size. Perhaps you need to make some adjustments for mutual interference.

Thanks @ROIMaison. That's what I figured. It's difficult to find much data on twin tails, which makes it difficult to compare computed tail volumes.

The engineer strives to give the aircraft a positive $c_{n_{\beta}}$ by adjusting the size of the vertical tail. A good value is $c_{n_{\beta}} = 0.1$ when the reference length is the wingspan, or $c_{n_{\beta}} = 0.2$ when the half span is used as reference length.
This is just a fancy way of saying that the aircraft should have natural weathervane stability and correct sideslip angles by turning into the wind. A fuselage by itself is mostly unstable, because the aerodynamic center of slender bodies is located close to their tip. Any side force on the fuselage will thus act ahead of the center of gravity. A compensating force acting behind the center of gravity is needed. Since not the forces themselves, but rather their moments around the center of gravity count, you cannot simply compare areas, but the product of area, lever arm and lift curve slope, which in turn is determined by the aspect ratio of the area concerned.
The higher aspect ratio of a vertical tail surface (higher at least when compared to the fuselage) will allow to make the tail smaller, but causes an earlier stall of the vertical tail. As a consequence, the stabilizing side force on the tail stops to increase at a sideslip angle where the destabilizing side force on the fuselage will still blithely increase with sideslip angle. To improve stability at high sideslip angles, strakes are added ahead of the vertical tail. Their surface will do little at small sideslip angles, but be very important at higher angles.
As you can see, comparing areas is not enough.


text:
Can biplane or triplane designs be revived with modern materials?
With the new-age technologies and cutting-edge composite materials etc available currently, is it possible that biplane and triplane designs will make a comeback in the near future?

Related

Biplanes (and triplanes) became (nearly) extinct not because high strength materials (like composites) were not available, but because they became available.
One of the major reasons for use of biplanes in the early days of aviation was that the materials available were of insufficient strength for the (wing) designs used.
The major disadvantage of biplanes (or triplanes) is aerodynamic- it produces a lot of drag compared to the monoplane and the wings interfere with each other.
So, the biplane was an (aerodynamically) inefficient solution to a structural problem. As higher strength materials like Aluminum became widespread, the biplanes fell out of favor.
While they can be revived, I don't see why someone would do that, except for nostalgia (or some special uses, like aerobatics).
There are some companies who manufacture or restore biplanes, but they usually don't use (modern materials like) composites, though modern avionics are used.

Biplanes can still see some (limited) use as bush planes: a much shorter wing can be helpful if you need to land in a narrow forest clearing, and they also have the advantage of good handling at low speeds (the AN-2, for example, which is still widely used today), but it's still a fact that they fulfill only special roles today, and not seeing more use is not because of the lack of technology.

@vsz: Part of the reason we don't widely use biplanes for bush planes is also because of advances in material science. Today planes can be built light enough with an engine powerful enough that they can have wingspans even smaller than WW1 era biplanes and yet only need a single wing. The Zenith CH 750 is a good example of this. Another good example is the Cri-cri

No.
Biplanes were the best way to take to the air in the early days because people had not wrapped their minds around the concept of a thick wing. All early aircraft used very thin airfoils, and a biplane produced a very lightweight and strong wing. Materials, by the way, had nothing to do with this, so the use of modern composite materials will not change the situation.
But a biplane does have advantages: If you

want the fastest possible roll rate,
a compact airframe,
want to fly slowly,
have little need for payload,

a biplane will be the right solution. However, as soon as the plane is used to earn revenue by transporting goods or people quickly and efficiently over long distances, the monoplane is by far the better solution.
Contraptions like the Blériot type 67 will never be built again (except maybe for entertainment).

Blériot type 67 bomber (picture source). Note the very thin wing airfoils.
On the other hand, for flying fun an EAA Biplane is hard to beat. And it is super easy to build.

EAA Biplane P2 (picture source). This design is possible with any aviation-rated materials.

Biplanes long survived in two niches. One was light weight for slow flying where the drag penalty is small, such as agricultural crop-spraying aircraft and ultralights. The other was where extreme maneuvrability demanded a compact layout but there was no need for ultimate speed, such as competition aerobatics.
Eventually modern materials came along and even these niches died out. When Paul MacCready designed his Gossamer Condor and Gossamer Albatross man-powered aircraft, he considered both braced biplane and braced monoplane layouts. Traditionally the braced monoplane carries higher structural forces so the equivalent biplane weighs less. For a man-powered aircraft that is a hugely significant advantage. But, using modern materials, MacCready found that the weight difference was so small that the aerodynamic efficiency of the monoplane won the day.

There is one niche that may be of interest for commercial application, a very large cargo lifter biplane.  Once wingspan reaches a certain length, even modern materials and designs reach limits due sheer size.
While 250 knots is considered extremely fast for a train, it is a long forgotten mode of travel for aircraft, with potentially enormous fuel savings.  Coast to coast in the USA would be 10 hours of flight time.  New York to Florida around 5 hours.
Combined with turboprops for regional next day cargo runs or mail, this could be a real money maker, with nostalgic appeal, and with safety in strength without the need for folding wings.  Passengers could also ride low budget.

Griffon Lionheart stagger wing composite with no struts first flew on 27 July 1997 Like the Beach stagger wing it used a R985. Only 3 made (Yellow company plane, white and blue) and production ended for kits 2001. Sounds like if more kits were made some tail changes were needed. Maybe some landing gear strengthening. "The owner/builder then applied left rudder, but the airplane continued to drift towards a runway sign. As they passed to the right of the sign the airplane pitched down violently, and nosed over. The airplane sustained substantial damage during the accident sequence to the left upper wing and the vertical stabilizer." Not sure if flaps down block tail action. "Probable Cause: The pilot's inadequate landing flare and subsequent loss of directional control during the landing roll."

Super Petrel LS Seaplane biplane Rotax engine model 912 is another composite. By Scoda Aeronautica in Brazil.

Elytron 2S tiltrotor biplane / Prandtl wing box. Experimental work in progress.

TVS-2DTS Honeywell TPE331-12U turboprop engine.Russian biplane to replace the AN-2 radial, AN-3 turboprop. Super nice plane. It is expected to fly at a maximum airspeed of 350 km/h and cover up to 4,500 km. The payload is calculated at 3.5 tons.

Welcome to Aviation! Please take the [tour] and read through the [help]. You'll find that this is a Q&A board not a general discussion forum. Somehow, somewhere, there is an answer in what you've written, but it's pretty well buried in the somewhat rambling description of an accident (or 2?). If you'll [edit] to focus what you've written into an answer to the OPs question (perhaps incorporating your comments into the answer itself), I think you'll have a good answer that will garner some up votes. As it stands, this will likely get deleted for not answering the question.